Conventionally, a photocurable resin composition having a high concealing effect has been widely used in a coating material for a flexible wiring board (see JP 2013-194156 A), a casting material for a replica of a prototype model (see JP H11-060962 A), a black stripe of lenticular lens (see JP 2013-082924 A), an adhesive agent for assembling an electronic equipment and the like (see JP 2014-025021 A), or the like. As a typical technique of imparting a concealing effect to a photocurable resin composition, mixing of carbon black of pigment can be mentioned. However, the concealing effect can be obtained, but most of active energy rays such as UV rays are absorbed into the carbon black, therefore, there has been a problem of causing poor curability when the concentration of the pigment is extremely high.
Under these circumstances, in JP H11-060962 A, there is a disclosure of a photosensitive resin composition for casting, which contains a photoradical polymerization initiator, a leuco dye having a characteristic of coloring with an acid, a photoacid generator, and an ethylenically unsaturated compound, and the cured product has excellent thick-film curability while being black. This utilizes the fact that the generation speed of the “radical species generated by light irradiation” is faster than the generation speed of the “acid generated by light irradiation”. That is, the photosensitive resin composition is cured by the transmission of light to the extent of the deep portion before being blackened with an acid.